Study of B0→D* -^π+π^-π+ and B0→D*-^K+π-^π+ decays

Using proton-proton collision data collected by the LHCb experiment at √s=7 TeV, corresponding to an integrated luminosity of 1.0 fb ^-1, the ratio of branching fractions of the B0→D* ^-π⁺π^-π⁺ decay relative to the B0→D*^-π⁺ decay is measured to be B(B0→D*^-π⁺π^-π⁺) B(B0→D*^-π⁺)=2.64±0.04(stat)±0. 13(syst). The Cabibbo-suppressed decay B0→D*^-K ⁺π^-π⁺ is observed for the first time, and the measured ratio of branching fractions is B(B0→D* ^-K⁺π^-π⁺)B(B0→D* ^-π⁺π^-π⁺)=(6.47±0. 37(stat)±0.35(syst))×10^-2. A search for orbital excitations of charm mesons contributing to the B0→D* ^-π⁺π^-π⁺ final state is also performed, and the first observation of the B0→D_̄1 ⁽²⁴²⁰⁾0π⁺π^- decay is reported with the ratio of branching fractions B(B0→(D_̄1 ⁽²⁴²⁰⁾0→D*^-π⁺) π^-π⁺)B(B0→D*^-π ⁺π^-π⁺)=(2.04±0.42(stat)±0. 22(syst))×10^-2, where the numerator represents a product of the branching fractions B(B0→D_̄1⁽²⁴²⁰⁾0π ^-π⁺) and B(D_̄1 ⁽²⁴²⁰⁾0→D*^-π⁺).